Technical Field
The invention relates to a power conversion technique, and particularly relates to a power conversion apparatus capable of opportunely discharging/draining electric energy stored in an X capacitor when supply of an alternating current input power is interrupted and a control chip thereof.
Related Art
Power conversion apparatuses are capable of converting an alternating current (AC) input power provided by a power company into a direct current (DC) output power. Therefore, the power conversion apparatuses are widely used/applied in electronic apparatuses such as computers, office automation equipment, industrial control equipment and communication equipment, etc.
Generally, an input stage of a conventional power conversion apparatus is equipped with an electromagnetic interference (EMI) filter to filter/suppress an EMI in the received AC input power. However, when supply of the AC input power received by the power conversion apparatus is interrupted, electric energy remained in an X-capacitor of the EMI filter probably results in a risk of electric shock when none discharge path exists. Therefore, based on security consideration, international safety standards have particular specifications: when the AC input power received by the power conversion apparatus is interrupted, the electric energy remained in the X-capacitor of the EMI filter equipped to the input stage of the power conversion apparatus has to drop to a safe voltage range within 1 second.
Therefore, a bleeder resistor is generally used to connect in parallel to two ends of the X-capacitor, and serves as a discharge path of the X-capacitor when supply of the AC input power received by the power conversion apparatus is interrupted. However, usage of the bleeder resistor inevitably causes a certain degree of power loss. Therefore, a power saving performance of the power conversion apparatus in a standby state is seriously influenced, which is not complied with an energy saving concept advocated by Energy star or other energy saving associations (such as CSA, DoE, EuP, etc.), or cannot satisfy a new standby power specification.